Turning Deadwood into Homes for Wildlife

Fallen and dying trees can be just as valuable as healthy live ones

12-01-1997
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Olwen Woodier

By planting trees on their property, homeowners can provide food, shelter and nesting sites for wildlife. But most people probably don't realize that fallen and dying trees can be just as valuable as healthy live ones. Decaying and standing dead trees, or snags as they are called, help to feed and house a wide variety of creatures. And like snags, piles of cut wood or branches can also provide refuges and food for small mammals, reptiles, amphibians, birds and butterflies.

"Some people think dead and dying trees look nasty or they're afraid they'll fall on their house so they take down the whole tree," says Kathy McNeil, a naturalist at Huntley Meadows Park in Alexandria, Virginia. "But snags are rich in fungal life and beetle larvae channels."

Beetles and other insects lay their eggs beneath the bark, where their larvae can feast on the soft wood. Their activities, along with the invasion of bacteria and fungi, hasten decay and help to loosen the bark. The insects attract woodpeckers and other birds. "It just takes a little effort for the creatures to break through the bark and find a big rotten hole," says McNeil. These holes can serve as nesting cavities for raccoons, squirrels, wood ducks and owls.

Snags are particularly important habitat for birds. According to studies conducted by the U.S. Forest Service, as many as 85 species of birds use dead trees in this country. Some, such as the brown creeper, are lured by the insect population and then nest beneath strips of loose bark. Others, like chickadees and woodpeckers, will excavate their own nest holes in soft, rotting wood.

"It's difficult for most species to excavate a cavity in a living tree," says reseacher Ron Rohrbaugh of Cornell University's Laboratory of Ornithology. "As the tree begins to die, the bark sloughs off and exposes the wood. When the wood softens with the decay and there's no layer of bark to get through, the tree becomes easier to excavate."

The type of bird attracted to a snag depends in part on the dead tree's location and the plant community that surrounds the tree.Bluebirds, for example, prefer to nest in snags in meadows and fields. Chickadees, titmice and house wrens not only nest in these open spaces but also along woodland edges and deeper into open woods. White-breasted nuthatches and woodpeckers prefer to nest in areas where there is a grouping of trees in orchards, woodland gardens or open, mixed woods.

Pileated woodpeckers (above) are a breed apart. They nest in holes they excavate annually in live trees or in snags located in old-growth woods or forests. "They will nest along woodland edges, although they prefer to nest in trees further into the forest," says Rohrbaugh.

Tall snags also attract birds of prey. The loftier branches provide outlook perches for owls and hawks. From such vantage points, the creatures can descend silently to snatch up prey.

Many mammals depend on dead trees, too. Gray squirrels, flying squirrels and raccoons compete for tree cavities in which they can raise their young and take shelter during the winter.

In all, some 80 animal species "actually depend on dead and dying trees, and hundreds more—including reptiles and amphibians—benefit from them," says Debbie Pressman, a biologist with the U.S. Forest Service who attempts to educate woodlot managers and others on the value of dead trees.

Given their value to wildlife, why not leave dead and dying trees standing in your yard? If you must cut a tree, however, consider some alternatives to removing it completely. You can, for example, cut the upper canopy branches and major side branches and leave the trunk. Or, if you can't leave the trunk standing, remove it and sink it into a hole two-feet deep in the ground near a woodland or meadow edge, a fence line or a hedgerow. As the trunk slowly decays and attracts insects, woodpeckers will probe for grubs and excavate holes that can be used by other cavity-nesting birds.

Another way to use cut tree trunks is to rest them horizontally on the ground in a woodland garden, along a shady walkway, in a tangle of weeds, among a patch of ground cover or by a pond. These trunks provide shelter and nesting sites to staghorn beetles, sow bugs, shrews, snakes, salamanders and a host of other small creatures. Fallen trees also provide feeding places for pileated woodpeckers and flickers.

If your backyard space is measured in yards rather than acres, you can erect a stack of logs or a brush pile to attract wildlife. Woodpeckers and songbirds will alight on a pile of unsplit logs, and overwintering butterflies will also take refuge in the chinks and cracks. Brush piles can also provide homes for many small animals. As the brush piles or logs break down into rotting wood, they attract more insects as well as amphibians and reptiles.

To create brush piles, crisscross tree thinnings or build them over a tree stump or discarded Christmas evergreen. If possible, stack them loosely about 6 feet high and 10 feet wide, so that birds can take cover within the pile. Birds inside or on top of the pile will leave droppings containing berry, grass and wildflower seeds. These little packages of moist fertilizer and seeds readily sprout and eventually produce a thicket of woody shrubs and vines. As the brush pile rots, the thicket will remain a refuge for wildlife.

If a brush pile in a suburban environment needs to be camouflaged for aesthetic reasons, create a narrow bed around the edges and plant wildflowers to attract hummingbirds, butterflies and other beneficial insects. By providing such habitats, you'll undoubtedly be pleased with the wide range of new life that takes advantage of the deadwood in your yard.